If you have a string instrument of any kind that needs fixing, a mistake you made in building a new instrument that you need to "disappear," or a question about the ethics of altering an older instrument, ask here. Please note that it will be much easier for us to help you decide on the best repair method if you post some pictures of the problem.

My cheapest bass has a very wide neck - Precision Style, which i simply do not like. Today i gave it a Bronco Bridge with somewhat narrower string spacing, and i want do reduce the width of the neck accordingly. About 3 mm at maximum; the nut width will not be changed.

I see two options:

a) remove the frets, make the neck narrower with a plane, chisels, rasp, belt sander,.... repair the chipped out pieces of the fingerboard. reinsert the frets, shorten them, and level them. I have done this before, and know what to expect. No router, no router plane because the would surely damage the open slots in the fretboards.

But i am notoriously lazy. So i think about variant

b) do everything with sanding tools.

i.e., leave the frets on, initally use the belt sander (grain 80), and of course take care the belt will run obliquely downward so the frets would be dragged into their slots. Less working steps, and the fret slots would remain filled.

In both cases the initial cuts would be done in an angle of 45 degrees; the final shape will achived later.

Possible or too dangerous? Or will the frets (nickel silver) be to strong for the sanding belt?

I'm lazy too.I'd use a sander, a spindle sander if you have one, or chuck one up in a drill press. I think a belt sander would give you less control, but it would probably work. I routinely use my oscillating spindle sander to shape the neck, and smooth off the fret ends after they're tapped in and cut with a nipper. It should be no trouble to go in a little farther to narrow the neck.

I'm going to leave it at its width, just thin starting from the fretboard and reach the full width at the body contact line. And find a smooth transition on the sides.I am definitely not going to cut into the body (what i did when i converted an SG kit into a tenor guitar).

I'd use an angle grinder with a 60 grit flap sanding disc to rough, and a coarse bastard file to finish, then normal techniques to reshape the neck. You can easily arrange to have the flap disc push the frets in towards the neck, and with an angle grinder you can keep it moving so the frets don't heat up too much.

I have often used a belt sander to "rough file" newly installed frets flush with the fingerboard. It's quick! just be sure to use light pressure so the sharp fret ends don't cut into the belt. Also, I usually clamp the belt sander upside down in a vise and bring the neck to the belt.

It can hardly be seen in the picture: the lower part of the neck heel has been left in its original with. So there is no loss in support.

But You're right, i should also re-fill the visible gaps especially the upper on the left/upper side. I think it'll be easier when i add some wood to the heel in the places where i sanded too much downward.

In this region i would probably need to find a better way to cut the upper part of the heel narrower. (I'll do that a 2nd time on another bass). Maybe with a chisel between the frets?